A Key to Larval Cestodes of Shallow-Water, Benthic Mollusks of … · 2012. 12. 11. · Some...

160 PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY

in particular Drs. W. M. Samuel and J. C.Holmes, for reviewing the manuscript. Thisstudy was supported in part by the NationalResearch Council of Canada (Operating GrantNo. A-6603), and the Boreal Institute forNorthern Studies.

Literatur e CitedAkhtar, S. A. 1947. A new genus of nematodes,

parasitic in the pika. Pavasitol. 38: 104-106.. 1956a. A new oxyurid (Nematoda:)

parasitic in the Baluch pika. Pakistan J. Sci.Res. 8: 95-96.

. 1956b. On the nematodes (family:Oxyuridae Cobb., sub-family: Labiostominaen. stibf.) parasitic in the pika of Alaska—Part I. Pakistan J. Sci. Res. 8: 133-139.

. 1958. On the nematodes (family:Oxyuridae Cobb., sub-family: Labiostominaen. subf.) parasitic in the pika of Alaska—Part II. Pakistan J. Sci. Res. 10: 56-62.

Anderson, R. C. 1958. Methode pour 1'examendes nematodes en vue apicale. Ann. de Para-sitol. 33: 171-172.

Erhardova-Kotrla, B., and M. Daniel. 1970.Parasitic worms of small mammals from themountain regions of the Eastern Hindu Kush.Folia Parasitologia (Praha) 17: 201-216.

Inglis, W. G. 1959. Some oxyurid parasites

(Nematoda) from Ochotona rufescens vizier(Mammalia: Lagomorpha) in Iran. Bull. Soc.Zool. de France 84: 178-187.

Lamberti, F., and S. A. Sher. 1969. A com-parison of preparation techniques in taxo-nomic studies on Longidorus africanus Merny.J. Nematodol. 1: 193-200.

Land, J. Van Der, and W. Templeman. 1968.Two new species of Gyrocotyle (Monogenea)from Hydrolagus affinus (Biito Capello)(Holocephali). J. Fish. Res. Bd. Canada 25:2365-2385.

Olsen, L. S. 1949. A new species of oxyuridnematode from a pika, Ochotona princepsfigginsi. Trans. Amer. Microsc. Soc. 68:337-341.

Seesee, F. 1973. The helminth parasites of thepika, Ochotona princeps (Richardson, 1828),in northern Idaho. Amer. Midi . Nat. 89: 257-265.

ShuPts, R. S. 1948. Novye nematody ot Alta-iskikh i Mongol'skikh gryzunov (Ochotonidae—pishchukhi). Doklady Akad. Nauk SSSR61: 173-176.

Spassky, A. A., and K. M. Ryzhikov. 1951.Gel'minty pishchukh Pribaikal'ya. TrudyGel'mintol. lab. Akad. Nauk SSSR 5: 34-41.

Steel, R. G. D., and J. H. Torrie. 1960.Principles and Procedures of Statistics. Mc-Graw-Hill, New York, 481 p.

A Key to Larval Cestodes of Shallow-Water,Benthic Mollusks of the Northern Gulf of Mexico

EDWIN W. CAKE, JR.Gulf Coast Research Laboratory, Ocean Springs, Mississippi 39564

ABSTRACT: Eleven distinct species of larval cestodes recovered from shallow-water, benthic mollusks ofthe northern Gulf of Mexico are differentiated in an illustrated taxonomic key. They represent ninerecognized genera in seven families of four orders and include the trypanorhynchs, Eutetrarhynchus sp.and Parachri&tianella sp., the tetraphyllideans, Anthobothrium sp., Dioecotaenia cancellata (Linton, 1890),Rhinehothrium sp., Acanthobothrium sp. (of Regan, 1963), Acanthobothrium sp. (of Harry, 1969), and"Scolex pleuronectis quadrilocularis"; the lecanicephalideans, Polypocephahis sp. and Tylocephalum sp.;and the diphyllidaen, Echinobothrium sp. Infected mollusks are widely distributed along the Gulf ofMexico coastline. Benthic marine mollusks serve as intermediate or paratenic hosts for these larvae whileelasmobranch fishes serve as final hosts.

Larval cestode parasites of shallow-water,benthic mollusks were collected during athree-year period from the eastern Gulf ofMexico (Florida Keys to the Mississippi Sound).During that study, 2,470 mollusks representing

36 gastropod species, 55 pelecypod species,and one octopus from 30 sampling localitieswere examined for larval cestodes. Elevendistinct species of larvae representing nine orten recognized genera in seven families and

Copyright © 2011, The Helminthological Society of Washington

OF WASHINGTON, VOLUME 43, NUMBER 2, JULY 1976 161

Table 1. Larval cestode parasites of shallow-water, benthic mollusks of the northern Gulf of Mexico.

Cestode larvae Gastropod hosts Pelecypod hosts

Order TrypanorhynchaFamily Eutetrarhynchidae

Eutetrarhynchus sp.

Parachristianella sp.

Order LecanicephalideaFamily Lecanicephalidae

Polypocephalus sp.

Family CephalobothriidaeTylocephdltim sp.

Order TetraphyllideaFamily Dioecotaeniidae

Dioecotaeniacancellata (Linton)

Family PhyllobothriidaeAnthobothrium sp.

Rhinebothrium sp.

Busycon spiratum pyniloides (Say)Crepidula fornicata (Linne)Fasciolaria lilium hunteria (Perry)Fasciolaria tidipa (Linne)Pleuroploca gigantea (Kiener)*Thais naemastoma canaliculuta (Gray)

Cantharus cancellarius (Conrad)Crepidula fornicata (Linne)Fasciolaria lilium hunteria (Perry)Fasciolaria tulipa (Linne)Polinices duplicatus (Say)

Busycon contraritim (Conrad)*Busy con spiratum pijruloides (Say)*Cantharus cancellarius (Conrad)*Crepidula fornicata (Linne)Crepidula maculosa ConradCrepidula plana SayFasciolaria lilium hunteria (Perry) *Fasciolaria tulipa (Linne) *Melongena corona (Gmelin)Murex florifer dilectus (A. Adams) *Murex fulvescens SovverbyMurex pomum (Gmelin) *Oliva sayana Ravenel*Pleuroploca gigantea (Kiener) *Polinices duplicatus (Say)Thais haemastoma canalicidata (Gray)*

Melongena corona (Gmelin)

Busycon contrariiim (Conrad)Busycon spiratum pyridoides (Say)*Cerithium atratum (Born)Cantharus cancellarius (Conrad)Crepidula fornicata (Linne )fCrepidula maculosa ConradCrepidula plana SayfFasciolaria lilium hunteria (Perry)

Argopecten irradians concentricus (Say)Atrina rigida (Lightfoot)Atrina seminuda (Lamarck)Dosinia discus (Reeve)

Anadara transversa (Say)Argopecten irradians concentricus (Say)*Atrina rigida (Lightfoot)Atrina seminuda (Lamarck)*Chione cancellata (Linne)Donax variabilis (Say)Macrocallista maculata (Linne)Macrocallista nimbosa (Lightfoot)*Noetia ponderosa (Say)Raeta plicatella (Lamarck)Spisula solidissima similis (Say)*

Argopecten irradians concentricus (Say)'

Anadara floridana (Conrad)Anadara transcersa (Say)*Anomia simplex OrbignyArea zebra (Swainson)Argopecten irradians concentricus (Say)*Artrina rigida (Lightfoot) *Atrina seminuda (Lamarck)*Chama macerophylla (Gmelin)Chione cancellata (Linne)Chlmnys sentis (Reeve)*Crassostrea virginica (Gmelin)*Cyrtopleura costata (Linne)*Dinocardium robustum (Lightfoot) *Donax variabilis (Say)Dosinia elegans Conrad*Ensis minor Dall*Laevicardium mortoni (Conrad)Macrocallista maculata (Linne)Macrocallista nimbosa (Lightfoot)*Mactra fragilis GmelinMercenaria campechiensis (Gmelin)*Merccnaria mercenaria tcxana (Dall)*Modiolus modiolus squamosus BeauperthuyNoetia ponderosa (Say)*Periglypta listen (Gray)*Pinctada imbricata RodingPinna carnea GmelinPseudochama radians (Lamarck)Pteria colymbus (Roding)Raeta plicatella (Lamarck)Spisula solidissima similis (Say)Spondylus americanus HermanTrachycardhim egtnontiamim (Shuttleworth)

[Anadara ovalis (Bruguiere)]fChione cancellata (Linne)

Anadara transversa (Say)*Argopecten irradians concentricus (Say)[Donax variabilis (Say)]fMacrocallista nimbosa (Lightfoot)Spisula solidissima similis (Say)Tellina versicolor DeKay

Amygdalum papryium (Conrad)Anadara transversa (Say)*Argopecten irradians concentricus (Say)'Atrina rigida (Lightfoot)\Atrina- seminuda (Lamarck)]fDonax variabilis (Say)Dosinia discus (Reeve)*fEnsis minor Dall



Table 1. Continued.

Cestode larvae Gastropod hosts Pelecypod hosts

Rliinebothrium sp.(continued)

Family OnchobothriidaeAcanthobotlirium sp.

(of Regan, 1963)

Acanthobothrium sp.(of Harry, 1969)

"Scolex pleuronectisciuadriloctdaris"

Unidentified Tetnvphyllideans"Scolex pleuronectis"

Order DiphyllideaFamily Echinobothriidae

Echinobothriiim sp.

Fasciolaria tulipa (Linne)*Melongena corona (Gmelin)Nassarius vibex (Say)Oliva saijana RavenelPleuroploca gigantea (Kiener)Polinices duplicatus (Say)

Busy con spiratum pijruloides (Say):::Cantharus cancellarius (Conrad)Fasciolaria lilium hunteria (Perry)*Fasciolaria tulipa (Linne)*Melongena corona (Gmelin)Murex pom-urn GmelinOliva saijana RavenelPleuroploca gigantea (Kiener) *fPolinices duplicatus (Say)[Thais haemastoma canalicidata (Gray)]f

Polinices duplicatus (Say)

Mactra fragilis GmelinNoetia ponderosa (Say)*f[Periploma inequale ( C. B. Adams)]fRaeta plicatella (Lamarck )fSpisula solidissima similis (Say)*Tagelus divisus SpenglerTagelus plebeius (Solander)Trachycardium egmontianum (Shuttleworth)

Argopccten irradians concentricus (Ensis minor Dall*[Macoma constricta (Bruguiere)]fPseudomiltha floridana (Conrad)Raeta plicatella (Lamarck)*Tagelus divisus Spengler*Tagehm plebeius (Solander)*f

(OCTOPOD)Octopus joubini Robson

Busycon. spiratum pyruloides (Say)Cantharus cancellarius (Conrad)Crepidula fornicata (Linne)Crepidula pinna SayFasciolaria lilium hunteria (Perry)Fasciolaria tulipa (Linne)Melongena corona (Gmelin)

Cantharus cancellarius (Conrad)Nassarius vibex (Say)

Anomalocardia auberiana (Orbigny)Argopecten irradians concentricus (Say)Chione cancellata (Linne)Cyrtopleura costata (Linne) *Dosinia discus (Reeve):::Dosinia eleganx ConradEnsis minor DallModiolus modiolus sqnamosits BeaupertlmyNoetia ponderosa (Say)

:;: Major intermediate or paratenie hosts.f Source: W. J. Wardle, Moody College of Marine Science, Texas A & M University, Galveston, Tex., pers. comm.

1975. Hosts enclosed in brackets were identified by Wardle only.

four orders were conditionally identified. Be-cause those larvae lacked taxonomically impor-tant characteristics, most could be identifiedonly to generic level. Recently developedartificial culture techniques facilitated genericidentification of several tetraphyllidean larvae(vide Read et al., 1960; Hamilton and Byram,1974). Improved culture methods and experi-mental infection studies may permit specificidentifications of many of these larvae in thefuture.

I have reviewed all known reports of ces-todes from benthic mollusks in the Gulf ofMexico and adjacent waters and a synopticreview is in press. The present taxonomic keyincludes all larval cestodes presently knownto infect benthic mollusks of the northern Gulf

of Mexico. William J. Wardle (Moody Collegeof Marine Science, Texas A & M University,Galveston, Tex., pers. comm., 1975) providedlarval cestode infection data from GalvestonBay and adjacent coastal mollusks, therebyextending the geographic range of this key. Alist of the molluscan hosts of each larval ces-tode included in this key is presented inTable 1.

This key should be used judiciously andwith the realization that it includes only thosecestodes recovered from benthic mollusks todate. Additional species of larval cestodesinfect squid, but those pelagic mollusks werenot examined during the study from which thiskey was derived. Bibliographic references areprovided within the key to facilitate specific



identifications should advanced specimens beencountered or eventually cultured by others.The cestode nomenclature follows that ofSchmidt (1970) with the exception of Antho-bothrium Beneden, which he splits, and Rhine-bothrium Linton, which he does not recognize.The molluscan nomenclature follows that ofAbbott (1974).

For the sake of convenience and clarity allcestodes covered by this key are consideredmetacestodes (a term for any larval formbetween the egg and adult) or larvae in thegeneral or collective sense. I have utilizedFreeman's (1973) system of metacestodeclassification in an attempt to avoid the presentconfusion in larval terminology. Freeman'ssystem utilizes descriptive prefixes (e.g.,acanthobothrio-, bothridio-, tentaculo-, uni-acetabulo-, etc.) in conjunction with standardmetacestode terms (e.g., procercoicl, plero-cercoid, cysticercoid, postplerocercoid, etc.) tocharacterize larvae.

Pelecypods appear to serve as primary inter-mediate hosts while molluscivorous gastropodsappear to serve as secondary intermediate orparatenic hosts for these larval cestodes. Othermarine organisms including crustaceans andfish may also be involved as intermediate hostsin the lif e cycle of some of these elasmobranchcestodes. Many of the molluscan hosts areconfirmed prey of demersal elasmobranchfishes of the Gulf of Mexico (Bigelow andSchroeder, 1953). Pelecypods become in-fected by ingesting reproductive products re-leased by definitive hosts (e.g., eggs and gravidproglottids) or free-swimming coracidia. Mol-luscivorous gastropods become infected by

ingesting infected pelecypods or gastropods.The first mode of infection is based on circum-stantial feeding and infection data (Cheng,1966) and the second mode was demonstratedduring this investigation (Cake, in press). Forthe parasitologist who is interested in surveyingthe cestode fauna of any coastal marine habitat,molluscivorous gastropods would serve as ideal"indicator" organisms (or cestode collectors).

Material s and MethodsBenthic marine mollusks were collected at

thirty Gulf coast localities between DryTortugas, Florida, and Bay St. Louis, Missis-sippi, from shallow, subticlal, estuarine andmarine environments (e.g., sand-, mud- andgrassflats and coral and oyster reefs, etc.) viaselective sampling methods (SCUBA, snork-ling, wading, shoveling, etc.). Based on pre-liminary parasite studies (Cake, 1972), largepelecypods (e.g., clams, oysters, pen shells,scallops, etc.) and molluscivorous gastropods(e.g., conchs, tulips shells, whelks, etc.) werecollected, maintained alive in large Styrofoamcontainers and transported to various coastallaboratories for dissection and examination.Again, based on preliminary studies, the fol-lowing tissues and locations were examined forcestode larvae: (in pelecypods) gills, labialpalps, stomach and stomach walls, intestine,intestine walls, and intestinal pouches (ifpresent), digestive gland and diverticula, andfoot musculature; (in gastropods) valve ofLeiblein (if present), esophagus and esoph-ageal pouches (if present), stomach and stom-ach wall, digestive gland and diverticula; and

Figures 1-6. Larval cestodes of Gulf of Mexico Mollusca. 1. Longicaudate, invaginated acanthoro-stellobothridio-cysticercoid of Echinobothrium sp. from Nassarius vibex. (Cut-away view showinginvaginated scolex.) 2. Scolex of Echinobothrium sp. from Ar. vibex. 3. Metabasal armature of internalsurface of tentacle of EutctrarJiynchus sp. tentaculo-neoplerocercoid from Pleuroploca gigantea. 4.Tentaculo-neoplerocercoid of Eutetrarhynchus sp. from /*. gigantea. 5. Side view of metabasal armatureof tentacle of Parachristianella sp. tentaculo-neoplerocercoid from Macrocallista nimbosa. 6. Tentaculo-neoplerocercoid of Parachristianella sp. from M. nimbosa.

Figures 7—12. Larval cestodes of Gulf of Mexico Mollusca. 7. Bothridio-postplerocercoid of Antho-bothriurn sp. from Anadara transversa. 8. Claviform capsule containing bothridio-postplerocercoid ofAnthobothrium sp. from A. transversa. (Cut-away view showing coiled postplerocercoid.) 9. Bothridio-plerocercoid of Acanthobothrium sp. (of Regan, 1963) from Oliva sayana. 10. Bothridio-plerocercoid ofAcanthobothrium sp. (of Harry, 1969) from Ensis minor. 11. Bothridio-plerocercoid of "Scolex pleuro-nectis quadrilocularis" from Octopus joubini. 12. Bothridio-plerocercoid of Rhinebothrium sp. fromArgopecten irradians concentricus.



1O 11



(in octopods) crop, stomach, intestine, digestivegland, and connective tissues in and aroundthe visceral mass.

Al l examinations were made using a stereo-scopic, dissecting microscope. When located,the larvae were removed or excised (if en-cysted), identified (usually to family or "type"),counted and either fixed and preserved orplaced in dishes of filtered seawater (at 30%osalinity and ambient temperature) for furtherobservations. Selected larvae of Acantho-bothrium spp., Rhinebothrium sp. and Polypo-cephalus sp. were incubated for up to 150 lirin a glucose-enriched, artificial elasmobranchsaline medium (vide Read et al., 1960;Hamilton and Byram, 1974). During incuba-tion some larval features (e.g., apical suckers)were lost or modified (quadriloculate totriloculate bothridial condition with terminalsuckers or pads), and some rudimentary adultfeatures developed (e.g., bothridial hooks).

The larvae were killed in an expanded orrelaxed condition with tepid tap water or hotAFA (ca. 50 C), fixed in AFA, and preservedin 70% ethanol and 5% glycerine. Large post-plerocercoids of Anthobothrium sp. were killedin an expanded and relaxed condition (all fourbothridia attached to bottom of dish) withliquid nitrogen and fixed and preserved asabove. The larvae were stained with eitherVan Cleave's combination hematoxylin orEhrlich's acid hematoxylin and mounted onslides via standard helminthological techniques.Illustrations of larvae were made with the aidof a micro-projector.

A Key to Larval Cestodes of Shallow-Water, Benthic Mollusks of the

Northern Gulf of Mexico

la. Scolex with two bothridia 2Ib. Scolex with four bothridia 4Ic. Scolex without bothridia 82a. Bothridia leaflike and spoon-shaped;

rostellum (myzorhynchus) armedwith a crown of apical hooks(DipViyllidea); longicaudate, invagi-nated acanthorostellobothridio-cysti-cercoid (Figs. 1 and 2); cysticercoidsembedded in digestive gland of small,omnivorous gastropods (Cantharuscancellarius and Nassarius vibex) ._.

Echinobothrium sp.

(Possibly E. musteli Pintner, 1889.)[Key to adult species: Rees, 1961.]

2b. Bothridia patelliform, each with pos-terior notch and two-armed protrusiletentacles (Trypanorhyncha) 3

3a. Tentacle armature heteroacanthousand homeomorphous, consisting en-tirely of small, falciform hooks ar-ranged in continuous, spiraling rows(Fig. 3); tentacle sheaths sinuous;tentaculo-neoplerocercoids (Fig. 4)encysted singly or in small groups(up to five per cyst) in muscularfolds of valve of Leiblein of Pleuro-ploca gigantea and other mollus-civorous gastropods

Eutetrarhynchus sp.[Keys to adult species: Dollfus, 1942;

Wardle and McLeod, 1952.]3b. Tentacle armature heteroacanthous

and heteromorphous (internal sur-face hooks large like rose thorns,others spiniform), arranged in spiral,half-turn rows (Fig. 5); tentaculo-neoplerocercoids (Fig. 6) commonlyencysted along intestine walls ofnumerous pelecypods (Table 1)

Parachristianella sp.[Description of Gulf of Mexico spe-

cies: Kruse, 1959.]4a. Bothridia simple, variable in shape

and without accessory suckers (Fig.7); apical sucker absent; bothridio-postplerocercoids encapsulated singlyin muscular, thin-walled, claviformcapsules (Fig. 8); small end of cap-sule embedded in visceral mass ofinfected pelecypods (Table 1); large,bulbous end containing coiled post-plerocercoid hangs free in host'smantle cavity Anthobothrium sp.

[Key to adult species: Wardle andMcLeod, 1952.]

4b. Bothridia multiloculate, apical suckerpresent 5

5a. Bothridia quadriloculate 65b. Bothridia not quadrilocuJate 76a. Bothridio-plerocercoids 3.4 to 6.2

mm long (Fig. 9); free in digestivetract of numerous molluscivorousgastropods (Table 1)_ _ __ Acanthobothrium sp. (of Regan, 1963)

(Possibly A. paulum Linton, 1890.)



6b. Bothriclio-plerocercoids 0.2 to 0.9mm long (Fig. 10); encapsulatedsingly or in groups (up to 150 perper capsule) in gut wall pouches ordistended digestive diverticula im-mediately adjacent to intestine ofsmall, burrowing pelecypods (Table1)__ Acanthobothrium sp. (of Harry, 1969)

(Possibly A. brevissime Linton, 1908.)[Key to adult species:

Goldstein, 1967.]6c. Bothridio-plerocercoids 0.4 to 1.5

mm long (Fig. 11); free or encap-sulated (in mucoid sheath) in diges-tive tract of Octopus joubini

"Scolex pleuronectis quadrilocularis'(Probably species of

Acanthobothrium.)7a. Bothriclia spoon-shaped, divided into

narrow anterior region with eighttransverse loculi and cuplike poste-rior region with eight radially ar-ranged loculi (Fig. 12) or leaf likewith up to 33 transverse loculi (Fig.13); small bothridio-plerocercoids,0.3 to 4.6 mm long, "confined" indigestive diverticula of numerouspelecypods (Fig. 12 and Table 1);larger (0.4 to 15.1 mm) and moreadvanced plerocercoids free in diges-tive tract of numerous, mollusci-vorous gastropods (Figs. 13 and 14,Table 1) Rhinebothrium sp.

[Review of genus: Campbell, 1970.]7b. Bothridia oval, slightly cupped; each

bothridium divided into 21 loculieither as three rows of seven each oras five central loculi surrounded by16 marginal loculi (Fig. 15); largebothridio-plerocercoids (ca. 8 mm)rare in stomach of Melongena coronaand digestive diverticula of Chionecancellata__ Dioecotaenia cancellata (Linton, 1890)

[Species description: Schmidt, 1969.]8a. Small (0.6 to 1.6 mm long) un-

encysted, uniacetabulo-plerocercoids(Figs. 16 and 17); scolex occasionallywith four bothridial precursors im-mediately posterior to apical sucker;osmoregulatory canals distinct; (earlytetraphyllidean plerocercoids) 9

8b. Small (0.1 to 0.4 mm long) encystedmetacestodes (Figs. 18 and 19);apical region of scolex protrusile,forming compact cushion or sucker,voluminous glandular mass, or ten-tacles; posterior scolex region with orwithout four simple suckers; (lecani-cephalidean metacestodes) 10

9a. Uniacetabulo-plerocercoids (Fig. 16)free in digestive tract of mollusci-vorous gastropods (Table 1) con-currently infected with advancedbothridio-plerocercoids of Acantho-bothrium sp.; probably early plero-cercoids of__ Acanthobothrium sp. (of Regan, 1963)

9b. Uniacetabulo-plerocercoids (Fig. 17)frequently confined in digestive di-verticula (tubules) of pelecypods(Table 1) concurrently infected withadvanced bothridio-plerocercoids ofRhinebothrium sp.; probably earlyplerocercoids of Rhinebothrium sp.

lOa. Scolex with muscular, cuplike apicalsucker, with protrusile, domelike pro-tuberance originating from suckerfloor; acaudate glando-procercoidssmall, 0.14 to 0.34 mm long, globose(Fig. 18); encysted singly in thick-walled cysts throughout visceral massof numerous pelecypods and in diges-tive gland of numerous gastropods(Table 1) Tijlocephalum sp.

[No key to adult species available;species list: Yamaguti, 1959.]

lOb. Scolex with 16, simple, unarmed,protrusile, apical tentacles and foursimple suckers (Fig. 19); tentaculo-plerocercoids small, 0.26 to 0.41 mmlong, thin and pyriform; encystedsingly in clumps of up to eight indi-viduals in thin, transparent capsulesin connective tissues of digestivegland in Argopecten irradians con-centricus Polypocephalus sp.

[No key to adult species available;species list: Yamaguti, 1959.]

Discussion

I have restricted this key to larval cestodesof benthic mollusks because more definitivedata are available on molluscan cestodes in theGulf of Mexico than on other invertebrate


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hosts, and because the collection and main-tenance of pelagic mollusks such as squid wasbeyond the scope of the investigation fromwhich this key was derived. That investigationwas designed to determine the cestode parasitesof resident mollusks rather than transient mol-lusks. Because most molluscan cestodes ex-hibit no host specificity (see Table 1), andbecause many molluscivorous gastropods arecapable of concentrating cestode larvae fromtheir prey, one may acquire definitive informa-tion on the cestodes of a particular coastalarea by studying molluscan hosts. That is notto say that other hosts (e.g., elasmobranchs)should not be examined. In most instances theadult cestode fauna of most coastal areas inthe Gulf of Mexico is well-known, but rela-tively littl e is known about their lif e cycles andintermediate hosts. This key was designedspecifically to assist those who wish to investi-gate the complete identities and lif e cycles ofthese molluscan cestodes.

In the body of this key I have suggestedspecific identities for several larval forms whichclosely resemble adult cestodes from the samearea. I am particularly indebted to Mr. TomMattis (Gulf Coast Research Laboratory,Parasitology Section, pers. comm., 1973-1975)for providing information on the elasmobranchcestodes of the northeastern Gulf of Mexico.The suggested identity of Echinobothrium sp.cysticercoids was based on scolex morphologywhich matches that of E. musteli Pintner, 1889,the only adult species reported from the north-eastern Gulf. The identities suggested for thetwo Acanthobothrium forms were based onmeristic comparisons of incubated plero-cercoids and adults (as reported in the liter-ature ).

The two trypanorhynch larval forms includedin this key appear to be undescribed species,and wil l be formally described in a subsequentpublication. Only one species of Eutetra-

rhynchus, E. lineatus (Linton), and two spe-cies of Parachristianella, P. monomegacanthaKruse and P. dimegacantha Kruse, have beenreported from the eastern Gulf of Mexico todate (Linton, 1908; and Kruse, 1959, respec-tively). The descriptions of those three eutetra-rhynchids do not match those of the larvalforms recovered from marine mollusks. Thereis a slight resemblance, however, between theParachristianella larvae recovered from penaeidshrimps (Kruse, 1959) and pelecypod mollusksin the vicinity of Alligator Harbor, Florida(Cake, 1972).

Regan (1963) and Harry (1969) recoveredand described unidentified tetraphyllideanlarvae from crown conchs, Melongena, corona,and channeled duck clams, Raeta plicatella, inFlorida and Texas, respectively. I obtainedliving specimens from the same gastropodhost and locality reported by Regan (1963),and from the same pelecypod host, but from adifferent locality than that reported by Harry(1969). I also obtained specimens of Harry'slarvae that he had given to James Byram(Brigham Hospital, Pathology Dept., Boston,Mass.). The plerocercoids that I collected arethe same as those described in the originalpublications. Subsequent incubation experi-ments by Hamilton and Byram (1974) and thisinvestigator revealed that those plerocercoidswere two distinct species, that they were inthe family Onchobothriidae, and that theybelonged in the genus AcanthobothriumBeneden. The onchobothriid plerocercoids re-covered from Joubini's octopus, O. joubini,probably belong in the same genus, but becausenone were incubated (in vitro) in artificialelasmobranch saline, that generic identity can-not be confirmed. That octopus does consumesmall pelecypods such as the hosts of the plero-cercoid reported by Harry (1969) (pers.observ.), and the two larval forms [Acantho-bothrium sp. (of Harry, 1969) and "Scolex

Figures 13-19. Larval cestodes of Gulf of Mexico Mollusca. 13. Bothridio-plerocercoid of Rhine-bolhrium sp. from Busycon spiratum pyruloides. 14. Contracted scolex (bothridia) of Rhinebothriumsp. from It. s. pyruloides. 15. Bothridio-plerocercoid of Dioecotaenia cancellata (Linton, 1890) from Chionecancellata. 16. Uniacetabulo-plerocercoid of Acanthobothrium sp. (of Regan, 1963) from Fasciolariatidipa. 17. Uniacetabulo-plerocercoid of Rhinebothrium sp. from C. cancellata. 18. Encysted, acaudateglando-procercoid of Tylocephalum sp. from Argopecten irradians concentricus. 19. Tentaculo-plerocercoidof Polypocehalus sp. from A. i. concentricus.



pleuronectis quadrilocularis"} do share meristicand morphologic characteristics.

The fact that the phyllobothriid plero-cercoids which infect numerous pelecypodsand gastropods are the same species of Rhine-bothrium was confirmed by artificial cultureand infection studies. The bothridial mor-phology of small plerocercoids from pelecypodsmatched that of advanced forms from mollus-civorous gastropods following incubation. Thetransfer of Rhinebothrium sp. plerocercoidsfrom pelecypod to gastropod hosts was demon-strated with artificial infection experimentsusing ponderous arks, Noetia ponderosa, andbanded tulips, Fasciolaria lilium hunteria.Those experiments wil l be detailed in a subse-quent publication.

Infection data obtained from hosts of twotetraphyllideans, Acanthobothrium sp. (ofRegan, 1963) and Rhinebothrium sp., stronglysuggest that the larvae which possess only anapical sucker and concurrently infect hostswith advanced bothridio-plerocercoids are infact early plerocercoids of those respectivespecies. The larvae fall within the sizeranges of the advanced plerocercoids; theyoccur simultaneously in the same hosts; andthey possess the distinctive osmoregulatorycanal systems of their respective advancedforms. Some of the larvae possess bothridialprecursors that range from undeveloped, darklystaining areas immediately posterior to theapical sucker to poorly developed, but definitebothridia.

Formal descriptions and analyses of infec-tion and occurrence data for all larval cestodescovered by this key wil l be published at alater date.

AcknowledgmentsI should like to express my appreciation to

Dr. R. W. Menzel (Florida State UniversityOceanography Department, Tallahassee, Fla.)and Dr. J. E. Byram (Peter Bent Brigham Hos-pital Pathology Department, Boston, Mass.,formerly with the F.S.U. Biological SciencesDepartment) for financial, logistical, and tech-nical assistance. Dr. W. J. Wardle (MoodyCollege of Marine Science, Texas A & M Uni-versity, Galveston, Tex.) and Mr. Tom Mattis(Gulf Coast Research Laboratory ParasitologySection, Ocean Springs, Miss.) kindly sharedtheir extensive knowledge of Gulf coast ces-

todes. Thanks are also extended to Dr. RobinOverstreet and Mr. Richard Heard (G.C.R.L.Parasitology Section) for critically reviewingthis manuscript.

Literatur e CitedAbbott 5 R. T. 1974. American seashells (2nd

eel.). Van Nostrand Reinhold Co. NewYork. 663 p.

Bigelow, H. B., and W. C. Schroeder. 1953.Fishes of the western north Atlantic. Part II ,Sawfishes, guitarfishes, skates and rays, p.1-514. Mem. Sears Found. Mar. Res. No. 1,Yale Univ., New Haven, Conn.

Cake, E. W., Jr. 1972. Larval and postlarvalcestode infections in several edible bivalvemollusks from the vicinity of St. Teresa,Florida. Nail. Shellfish. Assoc., Proc. 63:1(Abstr.).

. (In Press). Larval cestode parasites ofeastern Gulf of Mexico Mollnsca. I. Synopticreview. Gulf Research Reports.

Campbell, R. A. 1970. Notes on tetraphyl-lidean cestodes from the Atlantic coast ofNorth America, with descriptions of two newspecies. J. Parasit. 56: 498-508.

Cheng, T. C. 1966. The coracidium of thecestode Tylocephalum and the migration andfate of this parasite in the American oyster,Crassostrea virginica. Trans. Amer. Microsc.Soc. 85: 246-255.

Dolli'us, R. Ph. 1942. fitudes critiques sur lestetrarhynques du Museum de Paris. Arch.Mus. Nat. Histo. Nat., Paris 19: 1-466.

Freeman, R. S. 1973. Ontogeny of cestodesand its bearing on their phylogeny and syste-matics, p. 481-557. In Ben Dawes (ed.),Adv. in Parasit. Vol. 11. Academic Press.New York.

Goldstein, R. J. 1967. The genus Acantho-bothrium Van Beneden, 1849 (Cestoda:Tetraphyllidea). J. Parasit. 53: 455-483.

Hamilton , K. A., and J. E. Byram. 1974.Tapeworm development: the effects of ureaon a larval tetraphyllidean. T- Parasit. 60:20-28.

Harry } H. W. 1969. Anatomical notes on themactrid bivalve, Raeta plicatella Lamarck,1818, with a review of the genus Raeta andrelated genera. Veliger 12: 1-23.

Kruse, D. N. 1959. Parasites of the commercialshrimps, Penaeus aztecus Ives, P. duorarumBurkenroad and P. setiferus (Linnaeus).Tulane Studies in Zool. 7: 123-144.

Linton , E. 1890. Notes on Entozoa of marinefishes of New England with descriptions ofseveral new species. II . Ann. Rept. U. S.



Comm. Fish and Fisheries for 1887, Wash-ington, D.C. 15: 718-897.

— -. 1908. Helminth fauna of the DryTortugas. I. Cestodes. Carneg. Inst. Wash.,Publ. 102: 157-190.

Pintner, T. 1889. Neue Unterschungen ueberden Bau des Bandwurmkorpers. I. ZurKenntnis der Gattung Echinobothrium. Arb.Zool. Inst. Univ. Wien 8: 371-420.

Read, C. P., J. E. Simmons, Jr., J. W. Campbell,and A. H. Rothman. 1960. Permeationand membrane transport in parasitism: studieson a tapeworm-elasmobranch symbiosis. Biol.Bull. 199: 120-133.

Rces, F. G. 1961. Echinobothrium acanthino-phyllum, n. sp. from the spiral valve of Rajamontagui Fowler. Parasitol. 51: 407-416.

Regan, J. D. 1963. A cestode plerocercoidfrom the crowned conch. Q. T- Fla. Acad. Sci.26: 184-187.

Schmidt, G. D. 1969. Dioecotaenia cancellata(Linton, 1890) gen. et comb, n., a dioeciouscestode (Tetraphyllidea) from the cow-nosedray, Rhinoptera bonasus (Mitchell), inChesapeake Bay, with the proposal of a newfamily, Dioecotaeniidae. T- Parasit. 55: 271-275.

. 1970. How to know the tapeworms.Brown Co. Publishers. Dubuque, Iowa. 266 p.

Wardle, R. A., and J. A. McLeod. 1952. The/oology of tapeworms. Univ. Minn. Press,Minneapolis, Minn. 780 p.

Yamaguti, S. 1959. Systema helminthum. Vol.II . The cestodes of vertebrates. Interscience,New York. 860 p.

Small Dung Beetles as Biological Control Agents: LaboratoryStudies of Beetle Action on Trichostrongylid Eggsin Sheep and Cattle Feces1

R. C. BERGSTROM-, L. R. M/VKi 2 AND B. A. WERNERS

ABSTRACT: Four species of the genus Aphodius and Canthon practicola beetles were placed on sheepand cattle feces containing trichostrongylid eggs. Ten to 20 beetles were allowed to feed 1-5 days on5-100 g of feces containing 12-3,000 trichostrongylid eggs per g. Numbers of trichostrongylid eggs incultures with beetles decreased 24-90% more than in those without beetles within five days.

Researchers of Coleoptera have shown thatcoprophagous, scarabaeoid beetles are stronglyattracted to fresh feces of various animals(Fincher et al., 1970). Fincber et al. (1971)studied flight activities of several species ofbeetles during various hours of the day andfound a consistent periodicity of activity whichwas affected by temperature change.

Geographically nearer the present study arethe observations of McDaniel and Balsbaugh(1968) who showed that bovine manure isused as an overwintering medium for Coleop-

1 Published with the approval of the Director, Dr. NealHilston, University of Wyoming Agriculture ExperimentStation as Journal Article 796.

2 Division of Microbiology and Veterinary Medicine,University of Wyoming.

a Wyoming State Veterinary Laboratory, Laramie 82070.

tera in South Dakota; in the same state Kesslerand Balsbaugh (1972) noted a regular suc-cession of adult Coleoptera in bovine manureduring the growing season. Sanders andDobson (1966) reported on insects associatedwith bovine manure in Indiana. More recently,Waterhouse (1974) reported on the biologicalcontrol of dung by beetles and Fincher (1973)showed dung burying beetles could serve asbiological control agents of Ostertagia oster-tagia, a trichostrongylid nematode parasite ofcattle. Dung beetle mouth parts are efficientin macerating food and could be effective inbreaking nematode eggs in feces (Miller ,1961).

The objective of the present study was todetermine whether or not relatively small


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